World leaders have condemned the attack, calling it "barbaric," "cold-blooded" and "cowardly."

But illustrations are the symbols that remain most powerful because they are likely what led to Wednesday's attack in the first place.

To view the images of the controversial Charlie Hebdo covers depicting the Prophet Muhammad that are believed to be the motive behind the Paris terror attack, please click through to this story on The Huffington Post. Warning: The images may be offensive to some people.